1. Field
The present disclosure relates generally to aerospace vehicles and, in particular, to a method and apparatus for attaching thermal protection systems to an aerospace vehicle.
2. Background
A spacecraft is a type of vehicle or device designed for space flight. When a spacecraft returns to earth, the spacecraft may encounter high temperatures on reentry. A thermal protection system may cover some or essentially all of a spacecraft. A thermal protection system may protect the spacecraft from temperatures that may reach around 1650 degrees Celsius during atmospheric reentry. Further, this thermal protection system also may be used to protect the spacecraft from heat and cold in space while in orbit.
A thermal protection system may have different materials in different locations of the spacecraft depending on the amount of heat protection needed. For example, reinforced carbon-carbon may be used in the nose or leading wing edges of a spacecraft, such as a space shuttle. High temperature reusable surface insulation tiles may be used on the underside of an aircraft. Flexible insulation blankets, low temperature reusable surface insulation tiles, and other materials may be used for different locations on the spacecraft. Each type of thermal protection system may have specific heat protection, impact resistance, and weight characteristics.
It is desirable to have a thermal protection system that requires little or no maintenance. Some components used by a thermal protection system may include modular components that may be quickly removed and replaced. For example, tiles are examples of components that may be used in a thermal protection system. A tile is a thermal protection system component that may be fabricated from ceramic and/or ceramic matrix composite materials. More specifically, a tile may have, for example, a ceramic substrate with a ceramic matrix composite layer wrapped around the core. In the event that a tile may need to be replaced, it is desirable to minimize the amount of time needed to replace tiles on a spacecraft. For example, a vehicle turnaround time of around 48 hours or as little as two hours may be desirable.
Thermal protection systems on existing spacecraft may be adhesively bonded or mechanically attached. With bonded thermal protection systems, the amount of time and cost associated with installation, inspection, and/or repair may be much greater than compared to a mechanically attached system. Further, bonded thermal protection systems are not necessarily removable without destroying a portion of the part. As a result, inspection of a spacecraft substructure and/or internal spacecraft subsystems may be time consuming and expensive. Another drawback of bonded thermal protection systems is the temperature limitations of the adhesive bond lines.
Mechanical attachments may include, for example, a standoff or a carrier panel. A standoff thermal protection system may include stiffened panels encapsulating a back face insulation that is mechanically attached through flanges or metallic standoffs. A carrier panel thermal protection system may have tiles and/or blankets bonded to metal or composite carrier panels that are mechanically attached to a structure.
With mechanically attached thermal protection systems, increased weight may occur, which is undesirable with space operation vehicles. In some cases, the weight of a carrier panel on which the tile is mounted for attachment to a structure may be a large percentage of the total weight of the thermal protection system.
Therefore, it would be advantageous to have a method and apparatus that takes into account one or more of the issues discussed above as well as possibly other issues.